Method and system for exchanging earth energy between earthly bodies and an energy exchanger, especially to produce an electric current

ABSTRACT

An energy exchanger ( 2 ) is connected to an earth energy exchanger ( 18 ) via a flow line ( 10 ) and a return flow line ( 14 ). The flow line ( 10 ) and the return flow line ( 14 ) are both provided with a regulatable stop valve ( 12, 16 ). At least one heat-insulated flow pipe ( 20 ) is surrounded by a separation pipe ( 24 ) in a bore hole ( 22 ), whereby a return flow area ( 28 ) for circulatory water is connected thereto in a radially outward manner. The return flow area ( 28 ) contains at least one return flow pipe ( 30 ) connected to the return flow line ( 14 ) and a porous filling ( 38 ) in addition to being connected, at least on the base of the bore hole ( 22 ), to the lower inlet ( 46 ) of the flow pipe ( 20 ) or the lower inlets ( 46, 46   a ) of the flow pipes ( 20,20   a ) via one or several through openings ( 44 ) in the separation pipe ( 24 ). A connectable pressure medium device ( 56 ), and preferably a discharge valve ( 56 ) for discharging the circulatory water from the flow pipe ( 20 ) and triggering the production and transport of steam from the earthly body, is disposed on the flow line ( 10 ) between the stop valve ( 12 ) and the energy exchanger ( 18 ).

TECHNICAL FIELD

The invention relates to a method according to the preamble of claim 1and to a system for carrying out the method according to the preamble ofclaim 14.

PRIOR ART

Since the temperature in the earth's crust rises with an increasingdepth, it is possible, with sufficiently deep bores with a depth from,for example, 2000 m to generate hot steam, by means of which, forexample, a geothermal power station or a distant-heating system can beoperated. A method of this type is of considerable economic interest. Inwhat is known as the hot dry rock method (see, for example, BrockhausEncyclopedia, vol. 8, 19th edition, F. A. Brockhaus GmbH, Mannheim,1989, p. 337–338), the deep-seated heat from hot dry rocks is utilizedin that two bores of sufficient depth are sunk at a distance from oneanother, and water is forced down through one bore into artificiallywidened crevices and is pumped to the surface again through the otherbore as superheated water or as steam. Geothermal power stationsaccording to the dry steam principle are the simplest to operate, inwhich the superheated steam can be delivered directly to the turbineblades for the drive of generators. Substantial disadvantages of the hotdry rock method are the necessity for two separate bore holes, theartificial widening of crevices in the deep-seated rock and therequirement of a sufficiently hot rock zone. Systems for extraction ofearth energy from smaller depths than in the method initially mentionedare likewise known in many forms. Such systems utilize the earth energyat depths of 100 to 2000 m and above, in that, for example, circulatorywater flows out of the return-flow line of an energy exchanger through aporous filling as far as the bottom of a bore hole, is at the same timeheated and is led to the energy exchanger again by means of a pump viathe forward-flow line. However, the extraction of hot steam is notpossible by means of systems of this type.

PRESENTATION OF THE INVENTION

The object of the invention is to provide a method and a system for theextraction of hot steam from the deep-seated rock, in which thedisadvantages of the methods initially mentioned are avoided.

The object is achieved by means of:

-   -   a) the method as claimed in claim 1; and    -   b) the system as claimed in claim 14.

Since the return-flow pipes and the separation pipe are accommodated,together with the forward-flow pipe formed therein, in a single borehole, the drilling work to be carried out is reduced approximately tohalf, as compared with the hot dry rock method. Since the forward-flowregion and the return-flow region are connected to one another in thelower region of the bore hole via one or more passage orifices in theseparation pipe, and, finally, the lower region of the return flowcontains a porous filling, a closed system is possible, in whichvirtually no surrounding water penetrates and which manages essentiallywith the specific water quantity carried in circulation, with the resultthat a contamination of the circulation system is appreciably reduced.Thus, virtually no water has to be supplied to the system, and, on theother hand, virtually no water is lost to the surroundings after thestart-up, with the result that environmental pollution is substantiallyreduced. Since water also does not have to be supplied from thesurroundings, the contamination or the silting-up of the earth energyexchanger is avoided. Moreover, after the start-up of the system,demineralization of the circulatory water takes place as a result of therepeated evaporation, with the result that the risk of corrosion damagein the pipelines is appreciably reduced. After a particular operatingtime, the circulatory water can be purified in such a way that furtherpurification is necessary only at longer time intervals. This furthercontributes appreciably to cost reduction and operating reliability.

In the start-up phase, it may be expedient to supply fresh water and tocollect and demineralize in a collecting tank the circulatory waterwhich is contained in the system and is forced out. A further advantageis that improved heat exchange is achieved by means of the porousfilling in the return-flow region, so that there is no need to produceartificial crevices in the deep-seated rock. Yet another advantage isthat the system according to the present invention does not have tosatisfy any special requirements as to geological constitution, with theresult that, in turn, there are no special restrictions with regard tothe location of such a system.

Advantageous refinements of the method are described in claims 2 to 13and advantageous refinements of the system are described in claims 13 to35.

In general, before the system is put into operation, the earth energyexchanger contains circulatory water, for example flushing water orwater which has penetrated from the earthly body. The water columnpressure prevailing in the forward-flow pipe or forward-flow pipesprevents the removal of steam from the earth energy exchanger as long asthe water column pressure in the lower region of the forward-flow pipeor forward-flow pipes is higher than the steam pressure.

According to claim 2, at least one circulating pump may serve forstarting up the method, since even low pressure differences aresufficient to set the water columns in the return flow and in theforward flow in motion, with the result that the circulatory water inthe forward flow is increasingly heated and finally changes to steamgeneration.

To start up the method or the system, according to claims 3 to 9, thewater column in the forward-flow pipe or in the forward-flow pipes isforced out by means of a connectable pressure medium device. The steamgeneration which thereupon commences in the lower region of the borehole drives a circulatory process, in which circulatory water flows fromthe energy exchanger via the return-flow line and the return-flow pipeor return-flow pipes into the lower region of the bore hole, whereuponthe steam which occurs passes via the forward-flow pipe or theforward-flow pipes and the forward-flow line to the energy exchanger andthere, with energy being discharged, is returned to circulatory water.

The pressure medium to be introduced during the start-up may beintroduced, according to claim 4, in the upper region of theforward-flow pipe or, according to claim 5, in the upper region of thereturn-flow pipe. It is advantageous if the pressure medium isintroduced, preheated, according to claim 6, in order to accelerate thestart-up of the system. The pressure medium used may, according to claim7, be compressed air. It is also advantageous, according to claim 8, touse steam as the pressure medium, which is preferably obtained by animmersion heater being lowered into forward-flow pipe. It isparticularly advantageous, according to claim 9, to use water as thepressure medium.

In principle, during the start-up of the system, the circulatory waterto be forced out of the earth energy exchanger can be supplied to theearthly body by means of suitable passage orifices. The geological andecological disadvantages associated with this can be avoided by means ofthe refinement according to claim 10. In particular, the dischargedcirculatory water can be collected, purified and demineralized and, ifdesired, used further.

Good method conditions are obtained if, according to claim 11, work iscarried out with a temperature of the backflowing circulatory water oflower than 100° C. and preferably of 20° to 30° C. According to claim12, the forward-flow temperature of the steam to the energy exchangershould be at least 100° C., preferably 350° to 370°. Furtheradvantageous conditions are described in claim 13.

According to claim 15, the system may contain in the return-flow lineand/or in the forward-flow line a circulating pump which may serve, inparticular, for starting up the system, but also for operationalassistance.

In a refinement according to claim 16, it is also advantageous to startup the system by means of pressure medium. According to claim 17, thesystem for generation of pressure medium may be designed as a pressurepump. A refinement according to claim 18 is particularly advantageous,the pressure medium device used being an immersion heater which, bybeing lowered in the forward-flow pipe, evaporates the circulatory waterand thus generates the pressure medium.

According to claim 19, the circulatory water to be expelled from theforward-flow pipe during the start-up of the method or of the system isdischarged by suitable means above the earth's surface claims 20 and 21describe suitable discharge means. As already mentioned above, accordingto claim 22 a particularly preferred solution is to collect in acollecting tank the circulatory water which is to be expelled, in orderto free it of pollutants, thus leading to a solution protecting theenvironment or the system. The collected and purified circulatory watercan be supplied to the system again according to claim 23.

The refinement according to claim 24 is particularly advantageous forstarting up the system. After the closing of the shut-off valves in thereturn-flow and the forward-flow line and the shut-off valve between thefirst forward-flow pipe and the remaining forward-flow pipes, by thepressure medium device being connected at the first forward-flow pipethe circulatory water is initially forced downward in said forward-flowpipe, a corresponding water volume being forced out of the pipe systemthrough the remaining forward-flow pipes via the discharge valve. Afterthe first forward-flow pipe is drained in this way, the applied gaspressure also brings about the drainage of the remaining forward-flowpipes. Subsequently, the pressure medium device is disconnected, and thecirculation process driven by the steam power is set in motion by meansof the closing of the discharge valve and opening of the shut-off valvesin the return-flow and the forward-flow line and of the shut-off valvebetween the first forward-flow pipe and the remaining forward-flowpipes.

The refinement according to claim 25 reduces heat losses in theforward-flow pipe and can consequently increase the efficiency of thesystem.

It is conceivable, in principle, that only one return-flow pipe isarranged in the return-flow region. However, substantially betterresults can be achieved by means of a design according to claim 26,since, then, all the regions of the bore hole can be covered uniformlyand be utilized for energy extraction. The advantage of arranging aplurality of pipes in the forward flow and/or return flow is that thesystem can be operated at a plurality of speeds, depending on theconnection and disconnection of individual pipes.

A further improvement in efficiency is achieved by means of therefinement according to claim 27, in that heat exchange between thecirculatory water and the earthly body is prevented in the upper part ofthe bore hole, where the earth's temperature is lower than thetemperature of the circulatory water, whereas an increased heat exchangeis achieved in the lower part of the bore hole, where the earth'stemperature is higher than the temperature of the circulatory water.Moreover, as a result, the penetration of contaminated water from theupper earth strata into the bore hole is prevented.

A refinement of the system according to claim 28 is particularlyadvantageous, since a reduced flow resistance is achieved due to thepresence of passage orifices in the lower region of the separation pipeand since the forward-flow pipes are not formed in said region.

The necessary bore hole depth depends on the temperature profile in theearth's crust. In regions without pronounced geothermal anomalies, borehole depths of, for example, 2500 to 12 000 m according to claim 29 areexpedient. However, even greater depths are possible.

A further improvement in heat exchange between the circulatory water andthe earthly body is achieved by means of the formation of lateraldeflection bores in the refinement according to claim 30. Suchdeflection bores may be blind bores, but continuous bores are moreadvantageous, which again terminate in the bore hole. As a result, theheat-transmitting surface and consequently the performance of the earthenergy exchanger can be increased substantially. If such deflectionbores run essentially in the direction of the bore hole according toclaim 31, they are simpler to produce. In the arrangement radial to thebore hole according to claim 32, the deflection bores are located inzones of higher temperature and thus make it possible to have a highersteam energy with a smaller transmission surface.

The energy exchanger fed with the generated steam may be, according toclaim 33, a direct energy consumer or, according to claim 34, also aheat exchanger which heats a further circuit. The latter makes itpossible, in particular, to have a closed circulation process, in whichno pressure breakdown and therefore no precipitation of any minerals inthe circulatory water take place, with the result that silting-up of thesystem can be forestalled. The refinement whereby electrical current isgenerated is particularly advantageous. Such a system can be furtherimproved if heating heat is additionally produced, with the result thatthe temperature of the backflowing circulatory water is further loweredand the efficiency of the system is increased. Expediently, according toclaim 35, a turbine serving for driving a current generator is operatedby the ORC process, that is to say Organic Rankine Cycles.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention are described in more detailbelow with reference to the drawings, in which:

FIG. 1 shows a diagrammatic illustration of a system in verticalsection;

FIG. 2 shows a diagrammatic illustration of the pipe system of a systemin horizontal section II—II of FIG. 1 and on a larger scale,

FIG. 3 shows a diagrammatic illustration of the pipe system of a systemin horizontal section III—III of FIG. 1 and on a larger scale;

FIG. 4 shows a diagrammatic illustration of a modified system invertical section;

FIG. 5 shows a diagrammatic illustration of a modified line system ofthe system in FIG. 4 in vertical section;

FIG. 6 shows a diagrammatic illustration of a collecting tank forcirculatory water in vertical section;

FIG. 7 shows a diagrammatic illustration of a pressure medium device invertical section;

FIG. 8 shows a diagrammatic illustration of a system with circulatingpumps in vertical section; and

FIG. 9 shows a detail of an earth heat exchanger with radially runningdeflection bores in vertical section.

WAYS OF IMPLEMENTING THE INVENTION

FIG. 1 shows a system for the utilization of earth energy, for examplefor feeding an energy exchanger 2. The energy exchanger 2 consistspreferably of a multistage turbine 4, which drives a current generator6, and of an energy consumer 8 which is connected to the delivery lineof the turbine 4 and which may constitute, for example, a heating heatnetwork. The energy exchanger 2 is connected, via a forward-flow line 10with a regulatable shut-off valve 12 and via a return-flow line 14 witha regulatable shut-off valve 16, to an earth energy exchanger 18 whichcontains at least two heat-insulated forward-flow pipes 20 and 20 a in abore hole 22. The forward-flow pipes 20 and 20 a are surrounded by aseparation pipe 24 which has adjoining it, radially outward as far asthe bore hole wall 26, a return-flow region 28, in which return-flowpipes 30 are arranged. The bore hole region receiving the return-flowpipes 30 is sealing in the upper region 32, to a distance T₁ ofpreferably 2000 to 2500 m below the earth's surface 34, and is providedwith a porous filling 38, for example with gravel, in the lower regionas far as the bore hole floor 36. The walls of the return-flow pipes 30have, in the region of the porous filling 38, passage orifices 40 for animproved heat exchange, since the water and/or steam emerge from thereturn-flow pipes 30 into the porous filling, are further heated and canflow back into the return-flow pipes 30. A supply line 41 with ashut-off valve 43 is connected to the return-flow line 14, in order toadd water to the circulation process as required, for example in theevent of seepage or evaporation of circulatory water.

To increase the efficiency of the system, the region between theforward-flow pipes 20 or 20 a and the separation pipe 24 is filled withan insulating material 42. The forward-flow pipes 20 and 20 a terminateat a distance T₃ of preferably 400 m above the bore hole floor 36, andthe separation pipe 24 is provided, in the region therebelow, withpassage orifices 44. The forward-flow pipes 20 and 20 a communicate withone another in the region of their lower inlet orifices 46 and 46 a.

At the earth's surface 34, the first forward-flow pipe 20 is connectedto the forward-flow line 10. The second forward-flow pipe 20 a isconnected to the forward-flow line 10 via a regulatable shut-off valve48. A connectable pressure medium device 50 is designed, here, as apressure pump installation and consists of at least one pressure pump 52and of a regulatable connecting valve 54. This pressure pumpinstallation is connected to the forward-flow line 10 in the regionbetween the first forward-flow pipe 20 and the shut-off valve 12. Thepressure pump 52 is designed as a hydraulic pump for preferably hotwater and, if appropriate, as a compressor for compressed air. Adischarge line 55 having a discharge valve 56 is located in the regionof the forward-flow line 10 between the second forward-flow pipe 20 aand the shut-off valve 48.

Before the system according to FIG. 1 is put into operation, the earthenergy exchanger 18 contains, in general, circulatory water. As a resultof the connection between the return-flow pipes 30 and the forward-flowpipes 20 and 20 a in the lower region of the bore hole 22, the waterlevel in the forward-flow pipes 20 and 20 a is essentially at the sameheight as the water level in the return-flow pipes 30. The water columnpresent in the forward-flow pipes 20 and 20 a and in the return-flowpipes 30 prevents an extraction of hot steam. To start up the systemaccording to FIG. 1, the connectable pressure pump installation 50 isconnected to the first forward-flow pipe 20 as a result of the openingof the connecting valve 54, while the shut-off valve 48 between theforward flow pipes 20 and 20 a and the shut-off valves 12 and 16 of theforward-flow line 10 and of the return-flow line 14 are closed. The oldcirculatory water is thereby discharged from the forward-flow pipe 20through the second forward-flow pipe 20 a via the open discharge valve56. After the replacement of the old circulatory water by hot water hastaken place or after the drainage of the forward-flow pipes 20 and 20 aby means of compressed air, steam generation commences in the earthenergy exchanger 18. The pressure pump installation 50 is separated fromthe forward flow as a result of the closing of the connecting valve 54,the shut-off valve 48 is opened and the discharge valve 56 is closed. Bythe opening of the shut-off valve 16 in the return-flow line 14, as muchcirculatory water is supplied to the earth energy exchanger 18 as steamis discharged from the earth energy exchanger 18 through theforward-flow line 10 after the opening of the shut-off valve 12. Acirculation process driven by the steam power is consequently set inmotion. The temperature, pressure and/or quantity of the steam in theforward-flow line 10 is advantageously regulated by means of theregulatable shut-off valve 12. If a large amount of steam is extracted,the temperature of the steam falls and, conversely, the temperature ofthe steam rises when a small amount of steam is extracted. To improvethe heat exchange, the bore hole 22 can be provided, in the region belowa distance T₁, which may amount, for example, to at least 500 m, fromthe earth's surface, with lateral deflection bores 58 which, as shown,are designed as blind bores or, as indicated by dashes and dots,preferably as passage bores 58 a. They likewise contain a pipe 59, ifappropriate with holes 59 a in the wall, and are provided with a porousfilling 38 a. Such deflection bores 58 a may commence at 500 to 4000 mfrom the earth's surface and issue again a 2500 to 12 000 m into thebore hole 22 and serve for increasing the heat-transmitting surfaces.Only one such deflection bore may be present, but, expediently, aplurality of deflection bores arranged so as to be distributed aroundthe bore hole may be present.

FIG. 2 shows a diagrammatic illustration of the system according to FIG.1 in horizontal section II—II of FIG. 1 at depth of, for example, 1000to 12 000 m below the earth's surface 34. The bore hole has a diameter Dof, for example, 150 to 500 mm. The region within the separation pipe 24between the forward-flow pipes 20 and 20 a is filled with insulatingmaterial 42. In the annular region 60 of the bore hole 22 between theseparation pipe 24 and the bore hole wall 26 are arranged, for example,four return-flow pipes 30 distributed over the circumference. The cavityof the annular region 60 between the return-flow pipes 30 is filled witha porous filling 38. The wall of the return-flow pipes 30 is providedwith passage orifices 40.

FIG. 3 shows a diagrammatic illustration of the system according to FIG.1 in the horizontal section III—III of FIG. 1 in a depth region T₃ of,for example, up to 400 m above the bore hole floor 36. The separationpipe 24 is provided with passage orifices 44 and is free of forward-flowpipes and of insulating material and serves as a collecting space forthe steam.

The start-up of the system, that is to say steam generation, commencesat a temperature of above 100° C. The operating temperature for theenergy exchanger 2 is higher than 100° C. and is preferably 350° to 370°C. in the forward-flow line 10. In the multistage steam turbine 4 of theenergy exchanger 2, the steam is cooled to less than 100° C. andcondenses to form circulatory water which is supplied to the energyconsumer 8, for example a heat exchanger. In the heat exchanger, aforward flow 8 a of a consumer circuit is heated to about 90° C. and,after the discharge of heat, flows as return flow 8 b at approximately20° C. back to the heat exchanger. The result of this is that thecirculatory water leaves the heat exchanger 8 and consequently theenergy exchanger 2 at a temperature of about 25° to 30° C. and issupplied to the return-flow pipes 30 via the return-flow line 14.

FIG. 4 shows a system according to FIG. 1, although only oneforward-flow pipe 20 is formed. The return-flow region 28 is connectedto the lower inlet orifice 46 of the forward-flow pipe 20 in the lowerregion of the bore hole 22 via one or more passage orifices 44 a in theseparation pipe 24. Alternatively, the entire lower region of the borehole 22 is designed as is illustrated in FIGS. 1 and 3. The return-flowpipes 30 are combined into the return-flow line 14 which is provided, inthe region between the earth energy exchanger 18 and the shut-off valve16, preferably with a discharge valve 36 a to a discharge line 55.Furthermore, a supply line 41 with a shut-off valve 43 for the supply offresh water or recirculation water is connected to the return-flow line14. A connectable pressure medium device 50 a, which again is designedas pressure pump installation consisting of at least one pressure pump52 a and of a connecting valve 54 a, is connected to the forward-flowline 10 in the region between the earth energy exchanger 18 and theshut-off valve 12.

To start up the system shown in FIG. 4, with the shut-off valve 12 ofthe forward-flow line 10 being closed and with the shut-off valve 16 ofthe return-flow line 14 being closed, the pressure pump installation 50a is connected by the opening of the connecting valve 54 a. Thecirculatory water in the forward-flow pipe 20 is forced downward and isdischarged through the return-flow pipes 30 via the discharge valve 56 aabove the earth's surface 34. After the drainage of the forward-flowpipe 20 and filling with hot water have taken place, steam generationcommences in the earth energy exchanger 18. The pressure pumpinstallation 50 a is separated from the forward-flow line 10 by theclosing of the connecting valve 54 a and the discharge valve 56 a isclosed. By the opening of the shut-off valve 16 in the return-flow line14 and of the shut-off valve 12 in the forward-flow line 10, thecirculation process is set in motion by means of the steam power.

FIG. 5 shows the above-ground line system of the system of FIG. 4,although the connectable pressure medium device 50 b is not connected tothe forward-flow line 10, as in the example of FIGS. 1 and 3, but to thereturn-flow line 14 in the region between the earth energy exchanger 18and the shut-off valve 16. A discharge line 55 with a discharge valve 56b is connected to the forward-flow line 10 in the region between theearth energy exchanger 18 and the shut-off valve 12. In this case, tostart up the system, with the shut-off valves 12, 16 in the forward-flowline 10 and in the return-flow line 14 being closed, at least onereturn-flow pipe 30 and the forward-flow pipe 20 are drained or filledwith hot water by means of the pressure pump installation 50 b, with theconnecting valve 54 b open, the forced-out circulatory water running outvia the open discharge valve 56 b and the discharge line 55. As soon asthe operation has ended, the discharge valve 56 b and the connectingvalve 54 b must be closed. By the opening of the shut-off valve 12 ofthe forward-flow line 10, steam which has occurred can be conducted tothe energy exchanger 2. The circulatory water necessary for steamgeneration is made available by the opening of the shut-off valve 16 viathe return-flow line 14 and the return-flow pipes 30, if appropriatewith a pressure pump (not illustrated) temporarily being interposed,and/or from the earthly body in the lower region of the bore hole and/orvia a supply line 41 connected to the return-flow line 14 via a shut-offvalve 43.

In such systems, the circulatory water forced out of earth energyexchanger 18 via the discharge valve 56, 56 a, 56 b and the dischargeline 55 during the start-up of the system is preferably not dischargedinto the surroundings, but, according to the exemplary embodiment ofFIG. 6, is collected in a collecting tank 62. There, the circulatorywater 64 can be purified, for example freed of sludge 66 and bedemineralized and, if required, supplied anew to the circulation processvia the supply line 41 and the shut-off valve 43. The collecting tank 62may also serve, in general, for treatment, such as purification,demineralization, etc., of the circulatory water, should the result ofmeasurements indicate that the latter is too heavily contaminated forthe circulation process. Environmental pollution by the forced-out, atmost impure circulatory water is thereby avoided. Owing to thepurification and, if need be, treatment of the forced-out circulatorywater, optimally adjusted water can be supplied to the circulationprocess, as a result of which, on the one hand, the system itself isprotected from damage, in particular corrosion, and, on the other hand,the earthly body surrounding the earth energy exchanger 18 is protectedfrom damage caused by impurities.

FIG. 7 shows a further exemplary embodiment of a pressure medium device50 c which, instead of pressure medium, such as compressed air orpressure water, of the pressure pump installations of the exemplaryembodiments of FIGS. 1 to 4, evaporates the circulatory water 64 in theforward-flow pipe 23 and uses the steam as pressure medium for expellingthe circulatory water 64 out of the forward-flow pipe 20 b. The pressuremedium device contains an immersion heater 68 which is immersed into thecirculatory water 64 of the forward-flow pipe 20 b and which is guidedand centered in the forward-flow pipe by means of lateral guide elements70. The immersion heater 68 is suspended on a steel rope 72 which is ledthrough a pressure lock 74 in a closing cover 76 of the forward-flowpipe 20 b outward and, via a deflecting roller 78, to a winch 80. In asimilar way, an electrical supply line 82 of the immersion heater 68 isled outward through the pressure lock 74 and to a winch 86 via adeflecting roller 84. The two winches 80, 86 are driven in oppositedirections by a common drive motor 88 and a common transmission 90. Theimmersion heater 68 can follow the water level of the circulatory waterby means of the winches 80, 86, according to the progressive evaporationand progressive displacement of the circulatory water, until steamgeneration commences in the earth energy exchanger and the circulationprocess is set in motion. The immersion heater 68 can then be broughtback into the initial position by means of the winches 80, 86.

FIG. 8 shows the above-ground line system of the system of FIG. 5,although, instead of the connectable pressure medium device 50 b of FIG.5, a circulating pump 92 and 94 is arranged respectively in thereturn-flow line 14 and, if need be, in the forward-flow line 10. Adischarge line 55 with a discharge valve 56 b is again connected to theforward-flow line 10, specifically downstream of the circulating pump94. Furthermore, again, a supply line 41 with a shut-off valve 43 isconnected to the return-flow line 14. The energy exchanger 2 a is aclosed system which connects the system to a second circuit 96 with aforward-flow 96 a and with a return-flow 96 b which lead to one or moreenergy consumers, such as turbines (for example, for currentgenerators), heating arrangements and the like. In this case, theshut-off valves 12, 16 in the forward-flow line 10 and in thereturn-flow line 14 may be dispensed with. To start up the system, thecirculating pumps 92, 94 are switched on and the circulatory water iscirculating the system until it has been heated in such a way that,during the discharge of a part quantity of the circulatory water via thedischarge line 55 and during the pressure breakdown associated withthis, steam occurs in the circuit and circulation becomes automatic, sothat the circulating pumps 92, 94 can be switched off.

FIG. 9 shows the lowermost region of the bore hole 22 similar to theexample of FIG. 1, the lateral deflection bores 58 b not running in thedirection of the bore hole 22, but essentially radially thereto. Thedeflection bores 58 b emerge radially from the bore hole 22 above thebore hole floor 36, form a loop 98 and reenter the bore hole 22 near thebore hole floor 36. The deflection bore 58 b is again lined with a pipe59 having holes 59 a and is provided with a porous filling 38 a. Bymeans of this configuration, a large heat exchanger surface at an earthdepth having a high temperature is achieved.

List of reference symbols  2 Energy exchanger  4 Multistage steamturbine  6 Current generator  8 Energy consumer  8a Forward-flow  8bReturn flow 10 Forward-flow line 12 Regulatable shut-off valve 14Return-flow line 16 Regulatable shut-off valve 18 Earth energy exchanger20, 20a, 20b Forward-flow pipe 22 Bore hole 24 Separation pipe 26 Borehole wall 28 Return-flow region 30 Return-flow pipe 32 Sealing region 34Earth's surface 36 Bore hole floor 38, 38a Porous filling 40 Passageorifices in the return- flow pipe 41 Supply line 42 Insulating material43 Shut-off valve 44, 44a Passage orifices in the separation pipe 46a,46a Lower inlet orifice of the forward-flow pipe 48 Shut-off valve 50,50a, 50b, 50c Connectable pressure medium device (pressure pump) 52,52a, 52b Pressure pump 54, 54a, 54b Regulatable connecting valve 55Discharge line 56, 56a, 56b Discharge valve 58 Lateral deflection bore58a Lateral deflection bore 58b Lateral deflection bore 59 Pipe 59a Hole60 Annular region 62 Collecting tank 64 Circulatory water 66 Sludge 68Immersion heater 70 Guide element 72 Steel rope 74 Pressure lock 76Closing cover 78 Deflecting roller 80 Winch 82 Electrical supply line 84Deflecting roller 86 Winch 88 Drive motor 90 Transmission 92 Circulatingpump 94 Circulating pump 96 Second circuit 96a Forward flow 96b Returnflow 98 Loop

1. A method for exchanging energy between earthly bodies and an energyexchanger for current generation, the energy exchanger being connectedin a circulation process, via a forward-flow line for steam and areturn-flow line for circulatory water, to an earth energy exchangerwhich extends to a steam-generating depth of the earthly body,characterized in that, for forward flow and return flow in the earthlybody, use is made of a common bore hole, in which at least oneheat-insulated forward-flow pipe is surrounded by a separation pipewhich has adjoining it radially outward a return-flow region forcirculatory water which contains at least one return-flow pipe connectedto the return-flow line and, at least in the lower region, a porousfilling and which is connected to a lower inlet orifice of theforward-flow pipe at least at the floor of the bore hole via one or morepassage orifices in the separation pipe.
 2. The method as claimed inclaim 1, characterized in that the circulation process and consequentlysteam generation are set in motion by means of at least one circulatingpump.
 3. The method as claimed in claim 1, characterized in that, tostart up the circulation process, a water column located in theforward-flow pipe is forced out by means of pressure medium, until steamis obtained, and is present with predetermined nominal values at theenergy exchanger.
 4. The method as claimed in claim 3, characterized inthat the pressure medium is introduced in the upper region of theforward-flow pipe.
 5. The method as claimed in claim 3, characterized inthat the pressure medium is introduced in the upper region of thereturn-flow pipe.
 6. The method as claimed in one of claim 1,characterized in that a preheated pressure medium is used.
 7. The methodas claimed in one of claim 3, characterized in that the pressure mediumused is compressed air.
 8. The method as claimed in one of claim 3,characterized in that the pressure medium used is steam which isgenerated by the continuous evaporation of the water column in theforward-flow pipe by means of an immersion heater.
 9. The method asclaimed in one of claim 1, characterized in that the pressure mediumused is pressure water.
 10. The method as claimed in one of claim 3,characterized in that a circulatory water which emerges from theforward-flow pipe from the circulation process during the start-up ofthe circulation process is collected in a collecting tank and treatedand is used for topping up the circulation process as required.
 11. Themethod as claimed in one of claim 1, characterized in that circulatorywater having a temperature of below 100° C. is supplied to thereturn-flow pipe.
 12. The method as claimed in one of claim 1,characterized in that steam with a temperature of at least 100° C. issupplied to the energy exchanger.
 13. The method as claimed in one ofclaim 1, characterized in that the steam pressure which develops iscompensated in that a water column located above the steam in thereturn-flow region is forced downward in order to raise the temperatureand pressure, so that in the forward-flow region, at a depth of 7500 to12 000 m, steam with a pressure of, for example, 50 to 60 bar is formed,which flows via the preferably thermally insulated forward-flow regionto the energy exchanger.
 14. A system for carrying out the method asclaimed in claim 1, characterized in that the energy exchanger isconnected via a forward-flow line and a return-flow line for circulatorywater to an earth energy exchanger which has at least one heat-insulatedforward-flow pipe in a bore hole, the forward-flow pipe being surroundedin the bore hole by a separation pipe which has adjoining it radiallyoutward a return-flow region for circulatory water which contains atleast one return-flow pipe connected to the return-flow line and, atleast in the lower region, a porous filling and which is connected to alower inlet orifice of the forward-flow pipe at least at the floor ofthe bore hole via one or more passage orifices in the separation pipe.15. The system as claimed in claim 14, characterized in that acirculating pump is arranged in the return-flow line and/or in theforward-flow line.
 16. The system as claimed in claim 14, characterizedin that the forward-flow line and the return-flow line are provided ineach case with a regulatable shut-off valve, and a connectable devicefor generating a pressure medium for expelling the circulatory water outof the forward-flow pipe and consequently for triggering steamgeneration and steam conveyance is connected either to the forward-flowline between the shut-off valve and the earth energy exchanger or to thereturn-flow line between the shut-off valve and the earth energyexchanger.
 17. The system as claimed in claim 16, characterized in thatthe pressure medium device is designed as a pressure pump.
 18. Thesystem as claimed in claim 16, characterized in that the pressure mediumdevice is designed as an immersion heater capable of being lowered intothe forward-flow pipe.
 19. The system as claimed in claim 14,characterized in that means for the discharge of circulatory water outof the forward-flow pipe are present above the earth's surface.
 20. Thesystem as claimed in claim 19, characterized in that the discharge meanshave a discharge valve arranged in the return-flow line between theearth energy exchanger and the shut-off valve.
 21. The system as claimedin claim 19, characterized in that the discharge means have a dischargevalve arranged in the forward-flow line between the earth energyexchanger and the shut-off valve.
 22. The system as claimed in claim 19,characterized in that the discharge means have a collecting tank whichcontains preferably a supply line connected to the return-flow line. 23.The system as claimed in claim 14, characterized in that a supply linefor water is arranged on the return-flow line via a shut-off valve. 24.The system as claimed in claim 14, characterized in that the separationpipe has arranged within it at least one further forward-flow pipe whichcommunicates on the earth side with a first forward-flow pipe and whichis connected to the first forward-flow pipe at the earth's surface via ashut-off valve and has a discharge valve for the discharge of thecirculatory water capable of being expelled via the first forward-flowpipe through the second forward-flow pipe by means of the pressuremedium device.
 25. The system as claimed in claim 14, characterized inthat the region between the forward-flow pipe and the separation pipe isfilled by means of an insulating material.
 26. The system as claimed inclaim 14, characterized in that at least two, preferably a plurality of,return-flow pipes distributed around the separation pipe are arranged inthe annular region between the separation pipe and the bore hole wall.27. The system as claimed in claim 14, characterized in that the borehole region receiving the return-flow pipe is designed to be sealing inthe upper region, preferably from 1000 to 2500 m from the earth'ssurface, and is provided with the porous filling in the lower region asfar as the bore hole floor, the wall of the return-flow pipe beingprovided with passage orifices in the region of the porous filling. 28.The system as claimed in claim 14, characterized in that theforward-flow pipe terminates 400 m above the bore hole floor, and theseparation pipe is provided with passage orifices in this region. 29.The system as claimed in claim 14, characterized in that the bore holehas a depth T of 2500 to 12 000 m.
 30. The system as claimed in claim14, characterized in that the bore hole has at least one lateraldeflection bore which issues into the bore hole again in the region ofthe passage orifice of the separation pipe.
 31. The system as claimed inclaim 30, characterized in that the deflection bore runs essentially inthe direction of the bore hole.
 32. The system as claimed in claim 30,characterized in that the deflection bore runs essentially radially tothe bore hole.
 33. The system as claimed in claim 14, characterized inthat the energy exchanger has a multistage turbine which is connected toa current generator, the turbine preferably being followed by a furtherenergy consumer.
 34. The system as claimed in claim 14, characterized inthat the energy exchanger connects the earth's circulation process to asecond circulation process which contains a multistage turbine with acurrent generator.
 35. The system as claimed in claim 33, characterizedin that the turbine is designed to operate according to the ORC process.